To determine your maximum mortgage amount, lenders use guidelines called debt-to-income ratios. This is simply the percentage of your monthly gross income (before taxes) that is used to pay your monthly debts. Because there are two calculations, there is a "front" ratio and a "back" ratio and they are generally written in the following format: 33/38.

The front ratio is the percentage of your monthly gross income (before taxes) that is used to pay your housing costs, including principal, interest, taxes, insurance, mortgage insurance (when applicable) and homeowners association fees (when applicable). The back ratio is the same thing, only it also includes your monthly consumer debt. Consumer debt can be car payments, credit card debt, installment loans, and similar related expenses. Auto or life insurance is not considered a debt.

A common guideline for debt-to-income ratios is 33/38. A borrower's housing costs consume thirty-three percent of their monthly income. Add their monthly consumer debt to the housing costs, and it should take no more than thirty-eight percent of their monthly income to meet those obligations.

When preparing to buy a home, the first thing many homebuyers do is look at "homes for sale" ads in newspapers, magazines and listings on the internet. Some potential buyers read "how-to" articles like this one. The next thing you should do – before you call on an ad, before you talk to a Realtor, before you shop for interest rates – is look at your savings.

Why?

Because determining how much money you have available for down payment and closing costs affects almost every aspect of buying a home – including how you write your purchase offer, the loan programs you qualify for, and shopping for interest rates.

Mortgage Programs

If you only have enough available for a minimum down payment, your choices of loan program will be limited to only a few types of mortgages. If someone is giving you a gift for all or part of the down payment, your options are also limited. If you have enough for the down payment, but need the lender or seller to cover all or part of your closing costs, this further limits your options. If you borrow all or a portion of the down payment from your 401K or retirement plan, different loan programs have different rules on how you qualify.

Of course, if you have enough for a large down payment, then you have lots of choices.

A very important reason you need to have at least some idea of your down payment is for shopping interest rates. Some loan programs charge a slightly higher interest rate for minimal down payments. Plus, the interest rates for different loan programs are not the same. For example, conventional, VA, and FHA all offer fixed rate loans. However, the rates vary from one program to another.